The branch of psychology concerned with the diagnosis and treatment of psychological problems and disorders is called psychology.

I believe it called clinical psychology
clinical psychology is aimed to help patients in their personal development by helping them understand what actually cause them distress and help them alter their perception.
By doing this, the patients would be able to make an appropriate response when facing similar circumstances in the future.

It is called clinical psychology. It deals with mental and behavioral health. Clinical psychologists must identify, diagnose, monitor and solve psychological, emotional or behavioral issues with clients. Some of the more common disorders treated in this field include substance abuse, depression, anxiety, and eating disorders.